How to treat pets with cancer
Cancer has a similar behavior in pets as it has in humans. Our pets live in the same environment and are exposed to the same pollution as we are. As in humans cancer tumor is more frequent in older animals, and some cancer types seem to have a genetic predisposition.

Because nowadays many dogs and cats are family members and have an important social role, many clients want to know what kind of cancer their pet has, and if and how it can be treated. Having cancer does not mean to die from cancer in every case. Cancer is not cancer and many tumors can be treated and cured. Others are more aggressive and cure is not possible or unlikely. But nowadays more than half of the cancer can be cured.

Therapy is sometimes stress for the pet
It is our duty to inform clients about the behaviour of their pet’s cancer and its treatment and prognosis. This is done in close cooperation with the pet’s private veterinarians, as they know their patients best. But for detailed information, we need to see the animal and make some diagnostic tests.

An important role in the diagnosis lays in imaging procedures. They can help localize the cancer and determine the extent, such as metastasis. Therefore every animal will have chest radiographs. Lungs are the most frequent place for metastasis, and if we can find metastasis further diagnostic tests are usually no longer necessary.

Many of our patients have tumors in the head area. Here a classic radiograph is of limited value and computer tomography is often performed. This gives us the possibility to image the involved tissue in detail. Only when we know the exact extent we can decide on the ideal treatment.

The decision about treatment is made in close cooperation with the owner of the pet. It is important to include not only the cancer in the decision making, but also the condition, age, behaviour and character of the patient. A very nervous, anxious animal may not be a good candidate for an intense therapy and a more palliative treatment may be the better choice.

Sometimes we will not agree in treatment if the prognosis is very poor or the animal will have too many unacceptable side effects.

Treatment with linear accellerator
The gold standard therapy in almost every cancer is surgery, and every tumor which is operable will be operated. Besides surgery radiation therapy is the next most important treatment regime in humans and animals. Not only will the tumor be irradiated, but also a certain safety margin. Local side effects will be sunburn-like irritation of the skin for about two weeks and loss of hair. The hair will grow back within months, but mostly in a lighter color.

For radiation nowadays a linear accelerator is used. Its function is similar to a Rontgen machine, but the beam has a higher energy and is able to kill tumor cells. Depending on the type of tumor and its size, many animals can be cured.

Radiation therapy can also be used in a palliative fashion. There, the aim is not to cure, but to treat pain and simultaneously stabilize the tumor for a certain time period. These animals will have a good quality life for several months, sometimes even longer.

Because tumors occur naturally in our patients, we have the opportunity to study specific features of these tumors. A special feature we study is growth of new vessels (neovascularisation) before, during and after the therapy. We know that tumors can only grow if they are supported by a functional vascular system. Radiation therapy will not only kill tumor cells, it also will destroy vessels. We have evaluated the vascularity of tumors not only with imaging techniques, but also with molecular tests and how it is altered by radiation. Such studies are not easily performed in human medicine, but because of the similarity of cancer, results are extrapolated from our patients to humans.

Animals have a shorter life span than humans and therefore results are earlier available than from human experiments. New treatment regimes can be tested in our patients and results used for people. Such, both humans and animals can benefit, and less experimental animals may be needed.